The present invention relates to a combination drive assembly and particle trap for operatively engaging a plurality of accessory units and providing filtered fluid to the accessories under a positive head condition.
Pump drive assemblies for mechanically powering an accessory pump such as a steering pump and/or implement pump are well known. One type of known pump drive assembly includes a gear assembly support housing externally mounted to a transmission casing of a transmission with the input gear of the transmission utilized to drive the pump drive assembly. The accessory pump, as it is driven by the transmission, pumps transmission fluid through a dedicated line connected between the accessory pump and a flanged suction port provided on the transmission casing. The dedicated line may include a screen assembly spliced into the dedicated line to trap particles entrained in the transmission fluid before the fluid reaches the accessory pump.
The accessory drive assembly is typically mounted on the transmission casing at a position above the fluid level in the transmission so that the fluid does not unduly restrict rotation of the drive assembly in contact with the fluid. The gears of the accessory drive assembly are often pre-lubricated, during assembly, for example, with grease so that additional lubrication by the transmission fluid is not required. If fluid does enter the accessory drive assembly housing for any reason an amount of fluid may be trapped within the accessory drive housing and become significantly elevated in temperature which is known to cause gear failure or premature wear of the gears and bearings. To avoid compromising the accessory drive assembly, the accessory drive assembly is generally positioned away from the fluid to prevent problems caused by the interaction between the stagnant fluid and the gears.
The installation of the accessory drive assembly to the transmission generally includes, first, attaching the various drive assemblies so that the accessory pump is activated corresponding to rotation of the input shaft of the transmission. Second, at least one transmission fluid line must be installed between a flange on the transmission casing, below the level of fluid contained in the transmission casing, and the flange or connector on the accessory pump. Furthermore, a particle trap or filter screen is generally introduced within the transmission fluid to ensure that particles and debris entrained in the fluid are prevented from entering the accessory pump. Hence, installing an accessory pump and drive system requires multiple components and significant labor to equip a transmission with such a system.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention an accessory drive system to provide engagement between a driving input source and a driven accessory unit is provided and includes a housing attachable to the input source. A fluid suction port and a discharge port are defined by the housing and the suction port is in fluid communication with a fluid reservoir of the input source. The fluid discharge port is in fluid communication with the suction port and a gear assembly is rotatably supported by the housing. The accessory unit is operably engaged by the input source through the gear assembly and the gear assembly is structured and arranged within the housing to urge fluid away from the housing in response to movement of the gear assembly.
In another aspect of the present invention a method for operably engaging a fluid circulating accessory unit to an input source is provided and the method includes driving a gear assembly attached to the input source through a housing; circulating fluid from a reservoir to the accessory unit through the housing; and removing substantially all of the fluid entering a gear chamber of the housing through movement of the gear assembly within the housing.